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1、2012年3月,第l8卷,第1期,158—163頁(yè)高校地質(zhì)學(xué)報(bào)March2012,Vo1.18,No.1,P.158-163GeologicalJournalofChinaUniversities南祁連乙什春基性一超基性巖體LA—ICP—MS鋯石U—Pb年齡及其地質(zhì)意義余吉遠(yuǎn),李向民,馬中平,王國(guó)強(qiáng),唐卓,孫吉明,武鵬中國(guó)地質(zhì)調(diào)查局西安地質(zhì)礦產(chǎn)研究所,西安710054摘要:研究區(qū)位于中祁連地塊南緣,青海湖南一古雷深大斷裂南側(cè),是祁連成礦帶銅鎳礦找礦最有利地區(qū)。銅鎳礦礦體產(chǎn)于同源同期侵入的基性一超基性巖體內(nèi),銅鎳礦化無(wú)論在時(shí)間上和
2、空間上都與巖體的侵位密切相關(guān)。本次研究對(duì)乙什春基性一超基性巖體中的鋯石進(jìn)行了陰極發(fā)光(cL)成像觀察,結(jié)合Th/U比值特征,顯示其為巖漿成因;并應(yīng)用LA—ICP—Ms對(duì)鋯石微區(qū)u—Pb年齡進(jìn)行了測(cè)定,獲得乙什春含礦巖體中鋯石加權(quán)平均年齡為(455.1±1.7)Ma,表明其含礦巖體的侵位及礦化作用發(fā)生于晚奧陶世,成巖成礦的動(dòng)力學(xué)背景為陸緣裂谷構(gòu)造環(huán)境。關(guān)鍵詞:基性一超基性侵入巖;LA—ICP—MS;鋯石u—Pb定年;銅鎳礦;南祁連中圖分類(lèi)號(hào):P597.1文獻(xiàn)標(biāo)識(shí)碼:A文章編號(hào):1006—7493(2012)一0158—06Zirc
3、onU—PbDatingoftheYishichunMafic-UltramaficComplexFromSouthernQiliananditsGeologicalSignificanceYUdiyuan,LIXiangmin,MAZhongping,WANGGuoqiang,TANGZhuo,SUNJiming,WUPengxi’anInstituteofGeologyandMineralResource,ChinaGeologicalSurvey,Xi’an710054,ChinaAbstract:Thestudyarea
4、islocatedatthesouthernmarginoftheMiddleQilian,southoftheQinghaiLake-GuLeideepfaultbelt,whichisafavorableareaforcopper-nickeldepositsinQilianmetallogenicbelt.YishichunCopper-nickeloreoccurswithinthehomologousandcontemporaneousbasic—ultrabasicintrusions,andcopper-nicke
5、lmineralizationisspatiallyandtemporallyrelatedtotheintrusiverocks.Thecathodoluminescence(CL)imagesandtheTh/Uratiosofzirconsfromthebasic-ultramaficrockssuggestthatzirconcrystalsareofmagmaticorigin;TheLA-ICP-MSU-Pbdatingofthesezirconsyieldsaweightedmeanageof455.1±1.7Ma
6、.Therefore.theore—bearingrockemplacementandcopper-nickelmineralizationoccurredduringthelateOrdovician,andthemetallogenicdynamicprocesswasprobablyrelatedtoanancientcontinentalmarginrifting.Keywords:mafic—uhramaficintrusives;LA—ICP—MS:zirconU-Pbdating;Cu-Nideposit;Sout
7、hQilian;Firstauthor:YuJiyuan,MasterD.;E—mail:yujiyuanl11@163.con銅一鎳硫化物礦床主要分布在南祁連構(gòu)造帶的化1前言隆一青海湖裕龍溝一帶,在基性一超基性巖中還發(fā)祁連成礦帶中與基性一超基性巖有關(guān)的巖漿型現(xiàn)有拉水峽和裕龍溝小型銅鎳礦床以及乙什春、收稿日期:2011-10—08;修回日期:2011-11-14基金項(xiàng)目:青藏專(zhuān)項(xiàng)“北祁連成礦帶成礦條件研究與找礦靶區(qū)優(yōu)選”(1212010818090);中國(guó)地質(zhì)調(diào)查局大調(diào)查項(xiàng)目“北山一祁連成礦帶地質(zhì)礦產(chǎn)綜合研究”(12120100
8、10405)作者簡(jiǎn)介:余吉遠(yuǎn),1978年生,男,碩士,助理研究員,從事區(qū)域地質(zhì)、區(qū)域礦產(chǎn)調(diào)查研究;E-mail:yujiyuanl11@163.tom1期余吉遠(yuǎn)等:南祁連乙什春基性一超基性巖體LA—ICP—MS鋯石u—Pb年齡及其地質(zhì)意義159關(guān)藏溝、沙家等銅鎳